How one cell becomes two (mitosis)

Grade 7 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Two cards of a model animal cell, not to scale (model data: 4 chromosomes). Zee's friend says interphase is the first stage of mitosis, because the chromosomes are copied then. Which response is best?

   • Disagree: the chromosomes are copied in prophase, not in interphase
   • Agree: copying the chromosomes is how mitosis starts, so interphase is its first stage
   • Disagree: interphase comes before mitosis, when the cell grows and copies its chromosomes
   • Agree: interphase is a quiet resting time, so it is the first stage of mitosis

2. Read this first

   Use this

   Two cards of a model animal cell, not to scale (model data: 4 chromosomes). Card P: the 4 chromosomes sit in a line across the middle of the cell. Card Q: the copies of each chromosome are pulled into two groups, with 4 moving toward each end.

3. 2.

   Noah's friend says the chromosomes are pulled apart in metaphase and line up in anaphase. Which response is best?

   • Disagree: they line up in prophase and are pulled apart in metaphase
   • Agree: the pulling comes first, and then the chromosomes line up in the middle
   • Disagree: they line up in anaphase and are pulled apart in telophase
   • Disagree: they line up in metaphase and are pulled apart in anaphase
4. 3.

   not to scale (model data: 4 chromosomes). Pia's friend says each new cell must get only half of the chromosomes, or the number would double with every division. Which response is best?

   • Agree: each new cell has to make up the missing half after the split
   • Agree: each new cell gets half, because a full set would double the number in each cell
   • Disagree: the chromosomes are copied first, so each new cell gets a full set
   • Disagree: the chromosomes are not copied, so the new cells share the parent's set
5. 4.

   not to scale (model data: 14 chromosomes). Bo reads cards S and Q of one dividing model cell. How many chromosomes will each new cell hold, and which stage is card S?

   • 14 chromosomes; anaphase
   • 14 chromosomes; metaphase
   • 28 chromosomes; metaphase
   • 7 chromosomes; metaphase

6. Use this

   Cards for one dividing model plant cell, not to scale (model data: 12 chromosomes). Card P: the 12 chromosomes are thin, tangled threads inside a round nucleus. Card Q: a new wall is forming across the middle of the cell, making two cells, and each has its own nucleus.

7. 5.

   Jun follows the model plant cell on cards P and Q through mitosis and cytokinesis. How many chromosomes are in the two new cells together?

   • 12
   • 24
   • 48
   • 36
8. 6.

   after it divided, not to scale (model data). Esme reads that mitosis made two new cells with 10 chromosomes each. How many chromosomes did the cell have before it divided?

   • 10
   • 15
   • 20
   • 5

9. Use this

   Notebook about one model animal cell that starts with 4 chromosomes, model data. Line 1: In interphase, the cell grows and copies its chromosomes. Line 2: In metaphase, the chromosomes line up across the middle. Line 3: In anaphase, the copies are pulled apart, with 4 moving toward each end. Line 4: After cytokinesis, there are 2 cells with 2 chromosomes each.

10. 7.

    Kira writes four notebook lines about a model cell that starts with 4 chromosomes. Which line has a flaw?

    • Line 3: 2 chromosomes, not 4, should move toward each end
    • Line 2: the chromosomes line up in anaphase, not in metaphase
    • Line 1: the cell copies its chromosomes in prophase, not in interphase
    • Line 4: each new cell should have 4 chromosomes, not 2

11. Use this

    Notebook about one dividing model plant cell, model data. Line 1: In prophase, the chromosomes thicken and the nucleus boundary starts to break up. Line 2: In metaphase, the chromosomes line up across the middle. Line 3: In anaphase, the new wall is finished before the chromosomes reach the ends. Line 4: The two new cells have the same chromosomes as the first cell.

12. 8.

    Ari writes four notebook lines about a dividing plant cell. Which line has a flaw?

    • Line 2: the cell has already split in two by the time of metaphase
    • Line 3: the new wall forms after the chromosomes reach the ends
    • Line 4: the new cells should hold half of the chromosomes of the first cell
    • Line 1: the nucleus boundary stays whole until anaphase begins
13. 9.

    Each starting cell has 8 chromosomes. Ren sees that cell X's egg cells hold 4 chromosomes, but cell W's new cells hold 8. Does this break the rule that mitosis keeps the number?

    • No: cell X copied its chromosomes twice before dividing, so it ended up with 4
    • Yes: mitosis halves the number when a cell is making egg cells for the animal
    • Yes: mitosis sometimes halves the number of chromosomes, so the rule is wrong
    • No: egg cells come from a different division that halves the number, and mitosis keeps 8

14. Use this

    One card of a dividing model plant cell on a slide, not to scale (model data: 4 chromosomes). A new wall is just starting to form at the middle of the cell.

15. 10.

    Milo sees card Q: two nuclei in one plant cell, with a new wall just starting. A friend says the slide must be wrong. Which reply is best?

    • No: this is telophase, and cytokinesis finishes the division
    • Yes: each nucleus should hold 2 chromosomes, half of the 4
    • No: this is interphase, when the cell has copied its chromosomes
    • Yes: the cell must split as soon as the chromosomes are in two groups